Electronics &
Communication Technologies -
Glass to Metal Seals
Introduction
Glass to metal seals are vacuum tight assemblies, in
which metallic wires, tubes, eyelets or flanges are
firmly bound in a glass material. These are normally
used as insulated feed-throughs for electrical connections
in hermetically sealed devices and UHV systems as well
as mounts for electrodes, filaments etc. The materials
chosen have the properties of wettability by glass,
matched temperature coefficients of expansion and low
outgassing rates even at elevated temperatures making
them suitable for application in ultra high vacuum systems.
This technology has been developed for various types
of glass to metal seals- like flat bead seals, circular
bead seals, eyelet type seals, tubular seals, wafer
base seals and glass to metal feedthroughs for high
pressure applications. All these types of seals are
being produced in B.A.R.C. and are being used in several
in-house applications in the Department of Atomic Energy
and its research centres.
Technology being offered
Technology for the fabrication of FLAT BEAD SEALS and
CIRCULAR BEAD SEALS with the desired configuration of
pins is being offered at present. Along with this, the
design of mounting jigs and other fixtures will also
be given.
Specifically, (a) flat bead seals with five pins in
one line configuration in a glass bead of approximate
dimensions 23 mm x 6 mm x 4 mm. This type of seal is
presently being used as a mount for the electron emitting
filament and a shield plate in the mass spectrometer.
(b) circular bead seals with a diameter of 17 mm and
all the eight pins which are arranged in a configuration
suitable for mounting the three filaments of a thermal
ionization mass spectrometer.
Although technology being transferred covers only these
two specific types of seals, the recipient party of
this technology will be able to produce seals with any
desired pin configuration as required by the customer/user
after designing and making of necessary jigs and fixtures.
Applications
As electrical feed throughs and as insulating mounts
for hot filaments, electrodes etc. in instrumentation,
vacuum gauges, electronic devices and high / ultra high
vacuum systems.
Raw Materials Required
Special glass tubes of required sizes, Glass powder,
pins of iron-nickel cobalt alloy (Kovar or Fernico etc.),
LPG, Oxygen and cleaning chemicals.
Infrastructure Required
Controlled atmosphere furnace, annealing furnace, fabrication
facilities for making jigs and fixtures, wafer base
sealing machine, facility for working on glass (cutting,
polishing, blowing etc.), provision for acid cleaning
and disposal of cleaning fluids in a well ventilated
room of about 12’ x 12’ area.
Manpower
For a production capacity of approximately 1000 flat
bead seals per month two glass technicians are required.
Alternatively, these technicians can make about 500
circular bead seals (with straight pins in a desired
pin configuration) per month.
For further information please
contact :
Head,
Technology Transfer & Collaboration Division,
Bhabha Atomic Research Centre,
Trombay, Mumbai - 400 085
Tel : 091-022-25505337/25593897
Fax : 091-022-25505151
E-mail : headttcd@barc.gov.in
